Aqueous paint composition of baking-drying type

ABSTRACT

To propose a baking-drying water damping paint composition from which heavy film-thickness damping paint films can be obtained, heavy film-thickness damping paint films in which an inorganic filler is filled into the resinous component of paints to higher extent, and which are free from the occurrence of cracks and swelling in the paint films when the paint films are baked and dried.  
     The composition comprises a water emulsion including at least one first granular resin selected from the group consisting of styrene-butadiene copolymers, acrylic ester copolymers and ethylene-vinyl acetate copolymers whose glass transition temperature is from 0 to 20° C. and gel ratio is from 60 to 80%, and an inorganic filler in an amount of 200 parts by weight or more with respect to 100 parts by weight of said first granular resin. By using water emulsion particles whose gel ratio is controlled in the specific range, it is possible to obtain cured paint films which are free from the occurrence of cracks and swelling in the paint films and which exhibit a high damping effect stably even when the inorganic filler is filled to higher extent and the paint films are further dried at ordinary baking temperatures.

TECHNICAL FIELD

[0001] The present invention relates to a baking-drying water dampingpaint composition which is a water paint composition into which aninorganic filler is filled to higher extent, and which can form stableand heavy thickness cured paint films by baking.

BACKGROUND ART

[0002] Conventionally, sheet-shaped damping members, such as asphaltsheets, have been used in automotive body floors, doors, dashboards, andthe like, in order to give them a damping property. Moreover, coatingwater damping paints, which are adapted for automatically coating withrobots and so forth, have been developed recently. However, in the caseof ordinary damping paints, since the specific gravity of the resultingpaint films is smaller than that of asphalt sheets, it is necessary tofurther thicken the film thickness, and accordingly there is fear thatsuch problems might arise in that they interfere with the othercomponent parts, form steep irregularities on body floors, and so on. Inaddition, damping paints are yet highly expensive at present.

[0003] As a method to solve the problems, it is possible to think ofenhancing the specific gravity of paints by heightening the fillingratio of inorganic fillers into paints, however, when inorganic fillersare filled to higher extent, cracks are likely to occur in the resultingpaint films in baking and drying. As a result, there is a problem inthat the paint films come off from the substrates to be coated becauseof the poor adhesion to the substrates to be painted, and it is thusimpossible at present to fully effect the performance of paint filmswith inorganic fillers filled to higher extent.

[0004] In Japanese Unexamined Patent Publication (KOKAI) No. 8-209, 056,there is a disclosure on an ordinary-temperature drying water emulsionpaint which is good in terms of the adhesion to undercoatings and thedamping property. In the paint, 3 kinds of denatured resins, such as (a)a partially cross-linked acrylic resin whose gel ratio is from 10 to 90%by weight, (b) a carboxyl denatured styrene-butadiene rubber and (c) astyrene denatured acrylic resin, are mixed to use them at the same time,and it is considered preferable to compound an inorganic filler in anamount of from 150 to 250 parts with respect to 100 parts of theresinous content.

[0005] The paint is an ordinary-temperature drying one, and requiresdrying at room temperature for 72 hours in order to obtain a paint filmwhose film thickness is 5,000 μm in the examples. When it is baked athigher temperatures in order make the drying faster., it is assumed thata drawback arises in that no normal paint films can be obtained becausecracks, swelling and the like occur.

[0006] In Japanese Unexamined Patent Publication (KOKAI) No. 9-151,335,a water damping paint is disclosed which includes an inorganic filler inan amount of from 250 to 550 parts by weight and both or either one of athickening agent and a dispersing agent in an amount from 0.3 to 35parts by weight with respect to 100 parts by weight of the solid contentof a synthetic resin emulsion whose major component is a synthetic resinexhibiting a glass transition temperature of from −50° C. to 5° C. Thepaint was dried at room temperature in the examples. Nothing is setforth on the gel ratio of the synthetic resin.

[0007] In Japanese Unexamined Patent Publication (KOKAI) No. 5-194,906,there is a disclosure on a composition for water coating, compositionwhich comprises polymer fine particles, dispersed in a water medium, andan inorganic filler. The polymer fine particles are made of two kinds ofpolymer fine particles, i.e., synthetic rubber emulsion polymerparticles whose glass transition temperature is 0° C. or less andemulsion polymer particles whose glass transition temperature is 20° C.or more. Regarding the compounding amount of the inorganic filler intothe paint resin, a possibility of such a high compounding amount isdisclosed that it can preferably fall in a range of from 120 to 380parts by weight with respect to 100 parts by weight of the resinouscontent. However, it is considered appropriate that the thickness of thepaint falls in a range of from 200 to 800 μm, and when it is adapted forcompositions to be baked at elevated temperatures, it is recommended tocarry out 2-stage drying in which it is dried preliminarily at atemperature of from 60 to 100° C. and is thereafter baked at atemperature of from 120 to 160° C.

[0008] With the composition for water coating, it is difficult toovercome the drawback that cracks and swelling are likely to occur whenpaint films, which are applied in a heavy thickness, are baked and driedat high temperatures in one stage. The swelling limit of the paint filmsobtained in the examples was as thin as from 400 to 1,200 μm, andaccordingly it is not possible to obtain heavy thickness paint filmswhich are needed to obtain a damping property.

[0009] In Japanese Unexamined Patent Publication (KOKAI) No.2000-160,059, there is a disclosure on a water emulsion paint whichcomprises a water emulsion resin whose gel ratio is from 93 to 97% in anamount of from 20 to 50 parts by weight, and whose a baking temperatureis from 70 to 130° C. However, in the paint, since the resin is usedwhich exhibits such a high gel ratio, an inorganic filler is compoundedso that calcium carbonate, a filler, is compounded in an amount of 40%by weight at the highest with respect to 30% by weight of the resin asset forth in the examples, and thus the content of the inorganic filleris about 1.3 times the content of the resin at the highest. Since theresinous content exhibits a high gel ratio so that the cross-linkingdensity is enhanced therein, it is impossible to hold the filler in theresin when the inorganic filler is filled in the resin in a doubleamount or more of the resin, and accordingly cracks, swelling, and thelike, occur, and consequently it is difficult to obtain satisfactorypaint films.

[0010] When inorganic fillers are compounded in baking-drying waterpaints as described above, in the water paints disclosed conventionally,since there is a fear for cracked paints which are caused by thevolumetric contraction of paint films, volumetric contraction which isaccompanied by the evaporation of the water content within paints underbaking-temperature conditions where the drying of ordinary paint filmsis carried out, it has been usual practices to dry paints mostly in alow temperature range to make cured paint films, or to decrease thecompounding amount of inorganic fillers, or further to simultaneouslyuse special denatured resins in combination. In particular, wheninorganic fillers are filled to higher extent in order to reduce costsinvolved, there is a problem in that the phenomena, such as crackedpaint films and swollen paint films, arise remarkably in drying theaforementioned resinous components.

[0011] The present invention has been done in view of the aforementionedcircumstances, and it is an assignment to propose a baking-drying waterdamping paint composition, in which an inorganic filler is filled intothe resinous component of paints to higher extent, and from which heavythickness paint films being free from the occurrence of cracks andswelling in baking and drying the paint films can be obtained, in thefield of baking-drying water paints.

SUMMARY OF THE INVENTION

[0012] A baking-drying water damping paint composition according to thepresent invention comprises: a water emulsion including at least onefirst granular resin selected from the group consisting ofstyrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers whose glass transition temperature isfrom 0 to 20° C. and gel ratio is from 60 to 80%; and an inorganicfiller in an amount of 200 parts by weight or more with respect to 100parts by weight of said first granular resin.

[0013] Another baking-drying water damping paint composition accordingto the present invention comprises: a water emulsion including at leastone first granular resin selected from the group consisting ofstyrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers whose glass transition temperature isfrom 0 to 20° C. and gel ratio is from 60 to 80%, and at least onesecond granular resin selected from the group consisting ofstyrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers whose glass transition temperature isfrom 25 to 60° C.; and an inorganic filler in an amount of 200 parts byweight or more with respect to the sum of said first granular resin andsaid second granular resin taken as 100 parts by weight.

[0014] The present inventors found out that cracks occur in baking anddrying so that it is less likely to obtain heavy thickness paint filmswhose thickness is 3 mm or more when the gel ratio of the water emulsionincluding at least one first granular resin selected from the groupconsisting of styrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers is higher beyond 80%, and thatswelling occurs in baking and drying so that it is less likely to obtainheavy thickness paint films whose thickness is 3 mm or more when the gelratio of the water emulsion is less than 50% contrarily. Moreover, theinventors found out that, even when the gel ratio falls in a range offrom 60 to 80%, cracks or swelling occurs in baking and drying so thatit is less likely to obtain heavy thickness paint films whose thicknessis 3 mm or more when the glass transition temperature of the firstgranular resin is lower than 0° C. or when it is higher beyond 20° C.contrarily.

[0015] In addition, when a water emulsion is used which includes atleast one first granular resin selected from the group consisting ofstyrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers whose glass transition temperature isfrom 0 to 20° C. and gel ratio is from 60 to 80%, and at least onesecond granular resin selected from the group consisting ofstyrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers whose glass transition temperature isfrom 25 to 60° C., the present inventors found out that it is possibleto obtain paint films which have a heavy thickness equal to or more thanthe instance that a water emulsion is formed of the first granular resinalone.

[0016] The present baking-drying water damping paint composition hasbeen completed based on the discoveries and knowledge.

[0017] Said inorganic filler can preferably be at least one memberselected from the group consisting of calcium carbonate, talc,diatomaceous earth, barium sulfate, zeolite, magnesium carbonate andmica.

[0018] It comprises said inorganic filler in an amount of 200 parts byweight or more with respect to 100 parts by weight of said firstgranular resin. The upper limit can preferably be 600 parts by weightapproximately.

[0019] Moreover, the present baking-drying water damping paintcomposition can preferably be such that the drying-and-bakingtemperature falls in a range of from 70 to 160° C.

[0020] In the present invention, by using water emulsion particles whosegel ratio is controlled in the specific range, it is possible to obtainstable cured paint films which are free from the occurrence of cracksand swelling even when the inorganic filler is filled to higher extentand further the paint films are dried at ordinary baking temperatures.

[0021] Moreover, since the paint composition can enhance the specificgravity of paint films by enlarging the compounding amount of theinorganic filler, the thickness can be reduced compared with that ofconventional damping paints. In addition, since it is possible toutilize inexpensive inorganic fillers, it is possible to achievereducing the costs of damping paints so that it becomes a usefulbaking-drying water paint composition.

MODE FOR CARRYING OUT THE INVENTION

[0022] The present baking-drying water damping paint composition ischaracterized in that it can be baked and cured, and in that theinorganic filler can be compounded to higher extent. And, the firstgranular resin, water emulsion particles making the resinous componentof the paint composition, is composed of at least one member selectedfrom the group consisting of styrene-butadiene copolymers, acrylic estercopolymers and ethylene-vinyl acetate copolymers whose glass transitionpoint (Tg) falls in a range of from 0 to 20° C. Then, the first granularresin is characterized in that it is the resinous component whose gelratio, an index of the cross-linking density, falls in a range of from60 to 80%.

[0023] Moreover, the other present baking-drying water damping paintcomposition uses a water emulsion in which the first granular resin ismixed with the second granular resin selected from the group consistingof styrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers whose glass transition temperature(Tg) falls in a range of from 25 to 60° C.

[0024] It is necessary for the gel ratio to fall in a range of from 60to 80% in order that the inorganic filler is filled into the paintcomposition to higher extent so as to form satisfactory dried paintfilms under ordinary baking temperature conditions. When the gel ratioexceeds 80%, and when the inorganic filler is filled in a greateramount, it is not preferable because cured paint films are brittle sothat cracks occur in paint films. On the other hand, when the gel ratiois less than 60%, it is not preferable because the strength of paintfilms is not sufficient in baking and drying so that they cannotwithstand the rapid evaporation of the water and swelling occurs inpaint films.

[0025] Moreover, when the second granular resin whose glass transitiontemperature (Tg) falls in a range of from 25 to 60° C. is mixed in anamount of from 15 to 60% with respect to the first granular resin, it ispossible to promote the evaporation of the water content in initialbaking and drying so that the swelling of paint films is improved morein baking and drying, and accordingly it is possible to obtain curedpaint films provided with a good damping property and free from theoccurrence of cracks and swollen paint films even in baking and dryingpaint films with such an extremely heavy thickness as 8 mm in thickness.Note that the mixing of the first granular resin and second granularresin can be prepared with ease by mixing each one of first granularresin emulsions and second granular resin emulsions.

[0026] When the mixing amount of the second granular resin exceeds 60%of the sum of the first granular resin and second granular resin takenas 100%, or when the glass transition temperature (Tg) of the secondgranular resin exceeds 60° C., the formation of paint films is slow inbaking and drying so that paint films become brittle and cracks arelikely to occur. Moreover, when the compounding proportion of the secondgranular resin is less than 20%, or when the glass transitiontemperature. (Tg) is less than 25° C., the action of promoting theevaporation of the water content is insufficient in initial baking anddrying so that the swelling of paint films is likely to occur in paintfilms with such an extremely heavy thickness as 8 mm in thickness.

[0027] The first granular resin and second granular resin can be suchthat at least one or two members of styrene-butadiene copolymers,acrylic ester copolymers and ethylene-vinyl acetate copolymers are mixedto use, or, depending on cases, three of them are mixed to use. Thestyrene-butadiene copolymers can preferably contain butadiene in anamount of from 30 to 40% by weight at least. As for the acrylic estercopolymers, it is possible to utilize copolymers which are made from twoor more monomers selected from the group consisting of methyl acrylate,ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acryalte,2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate,glycidyl acrylate, and the like. The ethylene-vinyl acetate copolymerscan preferably be such that vinyl acetate is included in an amount offrom 40 to 50% by weight at least.

[0028] Moreover, in order to compound the inorganic filler to higherextent, it is preferred that the resinous component can be included inthe emulsion in a concentration of from 40 to 60% by weight because thepaintability is sustained and paint films which exhibit satisfactorypaint-film physical properties are formed after painting.

[0029] Since the resinous component in the water emulsions is providedwith the characteristics described above, it is possible to hold theinorganic filler even when the inorganic filler is compounded in thewater emulsions abundantly, and to let the sufficient paint-filmperformance reveal under ordinary baking-temperature conditions, namely,at a baking temperature of from 70 to 160° C.

[0030] The gel ratio designates the cross-linking density in resin, is ameasured value which designates how much insoluble components exist whenresin is immersed in solvent, and can be calculated by the followingequation.

((Weight of Dried Resin after being Extracted with Solvent)/(Weight ofResin before being Extracted with Solvent))×100

[0031] Specifically, the weight of the paint film which forms the driedpaint film of the water emulsion resin is measured, the paint film isimmersed in a solvent (for example, toluene), which can solve the resin,for a predetermined period of time, and the resinous paint film isthereafter dried at a predetermined temperature to measure the weight,and then the gel ratio is calculated by the above-describe equation.

[0032] In the present paint composition, the water emulsion resin whosegel ratio is from 60 to 80% can be prepared in general in the followingmanner. For example, when SBR is exemplified, SBR can be obtainedgenerally by subjecting styrene (S), butadiene (B), unsaturatedcarboxylic acid and the other monomers to emulsion polymerization in thepresence of an emulsifier. In the course of the emulsion polymerization,the water emulsion resin whose gel ratio is from 60 to 80% can beprepared by adding a chain transfer agent (underwater addition).

[0033] Note that it is possible to control the gel ratio by adjustingthe content of a cross-linking agent or a polymerization initiator alongwith the addition of a chain transfer agent. The water emulsion resin,the present first granular resin, exhibits a glass transition point (Tg)falling in a range of from 0 to 20° C. Moreover, the water emulsionresin, the present second granular resin, exhibits a glass transitionpoint (Tg) falling in a range of from 25 to 60° C.

[0034] Regarding the Tg as well, when SBR is exemplified likewise, it ispossible to obtain resins having a desired Tg by adjusting the contentsof styrene and butadiene.

[0035] In the case where a styrene-butadiene copolymer, an acrylic estercopolymer and an ethylene-vinyl acetate copolymer are used incombination, it is possible to carry out the forming by mixing theirwater emulsions which are synthesized independently.

[0036] As for the inorganic filler to be compounded, at least one ormore members selected from the group consisting of calcium carbonate,talc, diatomaceous earth, barium sulfate, zeolite, magnesium carbonateand mica are used. The compounding proportion into the paint compositionis 200 parts by weight or more, preferably from 200 parts by weight to600 parts by weight, further preferably from 200 to 400 parts by weight,with respect to 100 parts by weight of the resinous content.

[0037] When the compounding proportion of the inorganic filler is lessthan 200 parts by weight, it is not preferable because it cannot beturned into the present paint films in which the inorganic filler isfilled to higher extent. The upper limit of the compounding proportionof the inorganic filler can be allowed up to 600 parts by weight,however, can preferably be from 200 to 400 parts by weight approximatelyin order to make satisfactory paint films.

[0038] Moreover, in order to uniformly disperse and fill the inorganicfiller to sustain the strength of paint films, it is preferable to usethe inorganic filler whose average particle diameter is 50 μm or less.When the average particle diameter is 50 μm or less, the dispersibilityis enhanced in paint films to heighten the strength of paint films inbaking so that it is possible to inhibit the occurrence of cracks andswelling.

[0039] In addition, when inorganic short fibers, such as wollastoniteand whisker-shaped calcium carbonate, for example, whose fibrous lengthis from 100 μm to 1 mm are filled as the inorganic filler in an amountof from 30 to 100 parts by weight, it is possible to obtain satisfactorypaint films which are free from cracks and swelling, however, it isnecessary to care in order that clogged nozzles do not occur indischarging.

[0040] It is possible to adjust the qualities, such as the viscosity,for painting operations by compounding the paint composition with theother known additives, such as a defoaming agent, a dispersing agent, athickening agent and a running inhibitor agent.

[0041] The mixing of the paint composition can be carried out withhigh-speed dispersers which can stir and disperse it at a high speed,and accordingly it is possible to make pints having a viscosity andconcentration which are appropriate for painting operations.

[0042] The painting can be carried out with spraying guns for ordinaryspray painting, or by airless spraying methods.

[0043] Depending on the thickness, paint films coated on substrates tobe painted are usually baked and cured at a temperature of from 70° C.to 160° C. for from 5 to 30 minutes. Even when being dried under thebaking-temperature condition, no cracks, swelling, and the like, occurin the relatively heavy thickness paint films so that it is possible toform paint films, in which the inorganic filler is filled to higherextent, with ease. Note that the thickness of wet paint films beforebaking and the thickness of dried pained films after baking areidentical substantially. The lower the baking temperature is, thethinner the thickness of dried paint films tends to be. It is believedthat fine bubbles are dispersed in paint films when being baked atelevated temperatures.

[0044] The present dried paint films exhibit an enhanced specificgravity because the filling extent of the inorganic filler is high, andaccordingly can be used as damping paint films. Moreover, it is possibleto reduce the costs as damping paints, because inexpensive inorganicfillers can be compounded into paint films.

EXAMPLES

[0045] Hereinafter, it will be described specifically with reference toexamples.

Example No. 1

[0046] In the present example, a styrene-butadiene resin (SBR, Tg: 5° C.and a gel ratio of 80%) whose butadiene content was 35% was used as afirst granular resin, and an emulsion containing the resin in amount of55% by weight was used. Into the emulsion, calcium carbonate (an averageparticle diameter of 20 μm) as an inorganic filler, and a dispersingagent, a running inhibitor agent, and the like, were compounded asadditives in a predetermined amount, thereby preparing a paintcomposition recited in Table 1. Note that, as for the inorganic filler(calcium carbonate), those into which it was compounded in an amount of200 parts by weight and 400 parts by weight with respect to 100 parts byweight of the granular resin were prepared.

Example No. 2

[0047] Instead of the first granular resin of Example No. 1, astyrene-butadiene resin whose Tg was 5° C. and gel ratio was 70% wasused. The other components are the same as those of Example No. 1.

Example No. 3

[0048] Instead of the first granular resin of Example No. 1, astyrene-butadiene resin whose Tg was 5° C. and gel ratio was 60% wasused. The other components are the same as those of Example No. 1.

Comparative Example No. 1

[0049] Instead of the first granular resin of Example No. 1, astyrene-butadiene resin whose Tg was 5° C. and gel ratio was 90% wasused. The other components are the same as those of Example No. 1.

Comparative Example No. 2

[0050] Instead of the first granular resin of Example No. 1, astyrene-butadiene resin whose Tg was 5° C. and gel ratio was 50% wasused. The other components are the same as those of Example No. 1.

[0051] Table 1 sets forth the compounding composition of the respectivepaint compositions. Note that, in Table 1, they are designated as partsby weight of the water emulsion including water in an amount of 45%.

[0052] After the aforementioned respective compositions thus compoundedwere mixed by a high-speed stirrer to disperse, they were stirred todefoam, and were used as paints for application.

[0053] The paints were applied to a 70×150×0.8 (mm) electrodeposition-coated steel plate so as to be 50×150×3.0 (mm), immediatelyafter the application, they were put in a drying oven, whose temperaturewas controlled at 140° C., for 30 minutes to carry out baking anddrying. After the drying, the appearance of the paint films wasobserved, and the paint films free from cracks and swelling wereregarded as being passed (◯). Table 1 sets forth the results.

[0054] As recited in Table 1, in Example Nos. 1 through 3 whose wateremulsion particles (first granular resin) exhibited a gel ratio fallingin a range of from 80% to 60%, paint films in which the inorganic fillerwas compounded in an amount of 200 parts by weight and 400 parts byweight with respect to 100 parts by weight of the water emulsion (55parts by weight of the first granular resin) could form normal paintfilms when being baked at such a high temperature as 140° C.

[0055] However, in Comparative Example No. 1 whose water emulsionparticles exhibited such a high a gel ratio as 90%, cracks occurred inboth cases where the inorganic filler amount was 400 parts by weight and200 parts by weight. In Comparative Example No. 2 whose water emulsionparticles exhibited such a low a gel ratio as 50%, the strength of thepaint films was not sufficient so that swelling occurred in both caseswhere the inorganic filler amount was 400 parts by weight and 200 partsby weight, and they thus did not become normal paint films.

[0056] Therefore, when the gel ratio of the water emulsion particlesfalls in a range of from 80% to 60%, it is understood that, in paintfilms in which an organic filler is filled to higher extent and whosethickness is 6 mm (after being dried), paints can withstand thehigh-temperature baking at 140° C. for 30 minutes.

[0057] Moreover, on the samples from which the normal paint films wereobtained, the damping property (loss factor) by means of a cantilevermethod was measured. As for the measurement of the damping property(loss factor), they were applied to a 10×220 X 0.8 (mm) steelplate so asto be 1×200×3.0 in superficial density (after being dried), and were putin a drying oven, whose temperature was controlled at 140° C., for 30minutes to carry out baking and drying. After drying, the coated plateswere used as test plates for assessment, and were examined by acantilever method so as to calculate the loss factor at the secondaryresonance point by a half-width method. Table 1 sets forth the resultstogether with the measurement conditions. Since all of the paint filmsexhibited a loss factor of 0.1 or more, it is understood that they weregood as a paint film and could secure stable performance at ameasurement temperature of from 20° C. to 40° C.

[0058] From the results, in the present water paint composition, it ispossible to confirm that heavy thickness paint films can be obtainedeven under the high-temperature baking-drying condition.

Comparative Example No. 3

[0059] In the comparative example, a styrene-butadiene resin whose glasstransition temperature Tg was −5° C., gel ratio was 90% and butadienecontent was 43% was used, and an emulsion containing the resin in amountof 55% by weight was used. Into the emulsion, calcium carbonate (anaverage particle diameter of 20 μm) as an inorganic filler, and adispersing agent, a running inhibitor agent, and the like, werecompounded as additives in a predetermined amount, thereby preparing apaint composition recited in Table 2. Note that, as for the inorganicfiller (calcium carbonate), those into which it was compounded in anamount of 200 parts by weight and 400 parts by weight with respect to100 parts by weight of the SBR were prepared.

Comparative Example No. 4

[0060] Instead of the SBR of Comparative Example No. 3, astyrene-butadiene resin whose Tg was −5° C., gel ratio was 80% andbutadiene content was 43% was used. The other components are the same asthose of Comparative Example No. 3. Table 2 sets forth the specificcomposition.

Comparative Example No. 5

[0061] Instead of the SBR of Comparative Example No. 3, astyrene-butadiene resin whose Tg was −5° C., gel ratio was 60% andbutadiene content was 43% was used. The other components are the same asthose of Comparative Example No. 3. Table 2 sets forth the specificcomposition.

Comparative Example No. 6

[0062] Instead of the SBR of Comparative Example No. 3, astyrene-butadiene resin whose Tg was 30° C., gel ratio was 80% andbutadiene content was 28% was used. The other components are the same asthose of Comparative Example No. 3. Table 2 sets forth the specificcomposition.

Comparative Example No. 7

[0063] Instead of the SBR of Comparative Example No. 3, astyrene-butadiene resin whose Tg was 30° C., gel ratio was 60% andbutadiene content was 28% was used. The other components are the same asthose of Comparative Example No. 3. Table 2 sets forth the specificcomposition.

Comparative Example No. 8

[0064] Instead of the SBR of Comparative Example No. 3, astyrene-butadiene resin whose Tg was 30° C., gel ratio was 50% andbutadiene content was 28% was used. The other components are the same asthose of Comparative Example No. 3. Table 2 sets forth the specificcomposition.

[0065] After the aforementioned respective compositions thus compoundedwere mixed by a high-speed stirrer to disperse, they were stirred todefoam, and were used as paints for application.

[0066] The paints were applied to a 70×150×0.8 (mm) electrodeposition-coated steel plate so as to be 50×150×3.0 (mm), immediatelyafter the application, they were put in a drying oven, whose temperaturewas controlled at 140° C., for 30 minutes to carry out baking anddrying. After the drying, the appearance of the paint films wasobserved, and the paint films free from cracks and swelling wereregarded as being passed (◯). Table 2 sets forth the results.

[0067] As recited in Table 2, when the SBRs making the water emulsionparticles exhibited a glass transition temperature Tg of −5° C. or 30°C., no paint films which were free from defects and whose thickness wasas heavy as 5.0 mm were not obtained in all of the SBRs. In ComparativeExample No. 4, Comparative Example No. 5 and Comparative Example No. 8,3.0 mm and 4.0 mm paint films which were free from defects wereobtained. Even when the glass transition temperature Tg of the SBRs was−5° C. or 30° C., outside the range of from 0 to 20° C., it isunderstood that satisfactory paint films whose thickness was from 3 to 4mm approximately were obtained if the gel ratio was appropriate or ifthe compounding proportion of the inorganic filler was less.

[0068] On the samples from which the normal paint films were obtained,the damping property (loss factor) by means of the cantilever method wasmeasured. Table 2 sets forth the results together with the measurementconditions. Since all of the paint films exhibited a loss factor of 0.1or less depending on the measurement temperatures, it is understood thatthey could not secure stable performance as a paint film.

[0069] From the results, even when the gel ratio of the water emulsionparticles falls in a range of from 60% to 80%, it is understood that, ifthe glass transition temperature falls outside the range of from 0 to20° C., not only it is less likely to obtain satisfactorily heavythickness paint films, but also the temperature range in which a gooddamping property is exhibited is narrow even if they should be obtained.

Example No. 4

[0070] A water emulsion was obtained by mixing a water emulsion,containing a styrene-butadiene resin (SBR and Tg: 5° C.) whose gel ratiowas 80% and butadiene content was 35% in an amount of 55% by weight, inan amount of 80 parts by weight as a granular resin with another wateremulsion, containing a styrene-acrylic ester copolymer whose gel ratiowas 10% and Tg was 50° C., in an amount of 20 parts by weight as anothergranular resin. A paint composition was labeled as Example No. 4 inwhich an inorganic filler (calcium carbonate) was compounded in anamount of 400 parts by weight and a dispersing agent and a runninginhibitor agent were compounded in a summed amount of 20 parts by weightinto the resulting water emulsion.

Example No. 5

[0071] The compounding proportions of the granular resins of Example No.4 were changed so that an emulsion was used which was obtained by mixinga water emulsion, containing a styrene-butadiene resin (SBR and Tg: 5°C.) whose gel ratio was 80% and butadiene content was 35% in an amountof 55% by weight, in an amount of 50 parts by weight as a granular resinwith another water emulsion of a styrene-acrylic ester copolymer whosegel ratio was 10% and Tg was 50° C. in an amount of 50 parts by weightas another granular resin. The other compositions are the same as thoseof Example No. 4. The resulting paint composition was labeled as ExampleNo. 5.

Example No. 6

[0072] Instead of the water emulsion of Example No. 4, an emulsion wasused which was obtained by mixing a water emulsion, containing astyrene-butadiene resin (SBR and Tg: 5° C.) whose gel ratio was 60% andbutadiene content was 35% in an amount of 55% by weight, in an amount of80 parts by weight as a granular resin with another water emulsion of astyrene-acrylic ester copolymer whose gel ratio was 8% and Tg was 25° C.in an amount of 20 parts by weight as another granular resin. The othercompositions are the same as those of Example No. 4. The resulting paintcomposition was labeled as Example No. 6.

Example No. 7

[0073] The compounding proportions of the water emulsion particles ofExample No. 4 were changed so that an emulsion was used which wasobtained by mixing a water emulsion, containing a styrene-butadieneresin (SBR and Tg: 5° C.) whose gel ratio was 60% and butadiene contentwas 35% in an amount of 55% by weight, in an amount of 50 parts byweight as a granular resin with another water emulsion of astyrene-acrylic ester copolymer whose gel ratio was 8% and Tg was 25° C.in an amount of 50 parts by weight as another granular resin. The othercompositions are the same as those of Example No. 4. The resulting paintcomposition was labeled as Example No. 7.

Example No. 8

[0074] Instead of the water emulsion of Example No. 4, an emulsion wasused which was obtained by mixing a water emulsion, containing astyrene-butadiene resin (SBR and Tg: 5° C.) whose gel ratio was 80% andbutadiene content was 35% in an amount of 55% by weight, in an amount of80 parts by weight as a granular resin with another water emulsion of astyrene-acrylic ester copolymer whose gel ratio was 12% and Tg was 55°C. in an amount of 20 parts by weight as another granular resin. Theother compositions are the same as those of Example No. 4. The resultingpaint composition was labeled as Example No. 8.

Example No. 9

[0075] Instead of the water emulsion of Example No. 4, an emulsion wasused which was obtained by mixing a water emulsion, containing astyrene-butadiene resin (SBR and Tg: 5° C.) whose gel ratio was 80% andbutadiene content was 35% in an amount of 55% by weight, in an amount of90 parts by weight as a granular resin with another water emulsion of astyrene-acrylic ester copolymer whose gel ratio was 10% and Tg was 50°C. in an amount of 10 parts by weight as another granular resin. Theother compositions are the same as those of Example No. 4. The resultingpaint composition was labeled as Example No. 9.

Example No. 10

[0076] Instead of the water emulsion of Example No. 4, an emulsion wasused which was obtained by mixing a water emulsion, containing astyrene-butadiene resin (SBR and Tg: 5° C.) whose gel ratio was 60% andbutadiene content was 35% in an amount of 55% by weight, in an amount of40 parts by weight as a granular resin with another water emulsion of astyrene-acrylic ester copolymer whose gel ratio was 10% and Tg was 50°C. in an amount of 60 parts by weight as another granular resin. Theother compositions are the same as those of Example No. 4. The resultingpaint composition was labeled as Example No. 10.

Comparative Example No. 9

[0077] An emulsion was used which was obtained by mixing a wateremulsion, containing a styrene-butadiene resin (SBR and Tg: 5° C.) whosegel ratio was 90% and butadiene content was 35% in an amount of 55% byweight, in an amount of 80 parts by weight as a granular resin withanother water emulsion of a styrene-acrylic ester copolymer whose gelratio was 8% and Tg was 25° C. in an amount of 20 parts by weight asanother granular resin. The other compositions are the same as those ofExample No. 4. The resulting paint composition was labeled asComparative Example No. 9.

Comparative Example No. 10

[0078] The compounding proportions of the water emulsion particles ofComparative Example No. 9 were changed so that an emulsion was usedwhich was obtained by mixing a water emulsion, containing astyrene-butadiene copolymer (SBR and Tg: 5° C.) whose gel ratio was 90%and butadiene content was 35% in an amount of 55% by weight, in anamount of 50 parts by weight as a granular resin with another wateremulsion of a styrene-acrylic ester copolymer whose gel ratio was 8% andTg was 25° C. in an amount of 50 parts by weight as another granularresin. The other compositions are the same as those of Example No. 4.The resulting paint composition was labeled as Comparative Example No.10.

[0079] Table 3 sets forth the compounding composition of the respectivepaint compositions of aforementioned Example No. 4 through Example No.10 as well as Comparative Example Nos. 9 and 10. After the respectivepaint compositions were mixed by a high-speed stirrer to disperse, theywere stirred to defoam, and were used as paints for application.

[0080] The paints were applied to a 70×150×0.8 (mm) electrodeposition-coated steel plate so as to be 50×150×3.0 (mm), immediatelyafter the application, they Were put in a drying oven, whose temperaturewas controlled at 140° C., for 30 minutes to carry out baking anddrying. After the drying, the appearance of the paint films wasobserved, and the paint films free from cracks and swelling wereregarded as being passed (◯). Table 3 sets forth the results.

[0081] As recited in Table 3, in Example Nos. 4 through 7 in which awater emulsion whose glass transition temperature (Tg) was 5° C. and gelratio was from 80 to 60% was mixed in an amount of from 80 to 50 partsby weight as a granular resin with another water emulsion whose glasstransition point (Tg) was from 25° C. to 50° C. in an amount of from 20to 50 parts by weight as another granular resin, normal paint filmswhich had such a heavy thickness as 8.0 mm could be formed when paintfilms in which the inorganic filler was compounded in an amount of 400parts by weight with respect to 100 parts by weight of the granularresins were baked at such a high temperature as 140° C.

[0082] In Example No. 8 in which a water emulsion whose glass transitiontemperature (Tg) was 5° C. and gel ratio was 80% was mixed in an amountof 80 parts by weight as a granular resin with another water emulsionwhose glass transition temperature (Tg) was 55° C. in an amount of 20parts by weight as another granular resin, a paint film which had athickness of 5.0 mm could be obtained, but cracks occurred in paintfilms which had such a heavy thickness as 6.0 mm or more.

[0083] In Example No. 9 in which a water emulsion whose glass transitiontemperature (Tg) was 5° C. and gel ratio was 80% was mixed in an amountof 90 parts by weight as a granular resin with another water emulsionwhose glass transition temperature (Tg) was 50° C. in an amount of 10parts by weight as another granular resin, a paint film which had athickness of 6.0 mm could be obtained, but swelling occurred in paintfilms which had such a heavy thickness as 7.0 mm or more.

[0084] In Example No. 10 in which a water emulsion whose glasstransition temperature (Tg) was 5° C. and gel ratio was 60% was mixed inan amount of 40 parts by weight as a granular resin with another wateremulsion whose glass transition temperature (Tg) was 50° C. in an amountof 60 parts by weight as another granular resin, a paint film which hada thickness of 5.0 mm could be obtained, but cracks occurred in paintfilms which had such a heavy thickness as 6.0 mm or more.

[0085] From the facts, when the mixing amount of the granular resin ofthe water emulsion whose glass transition temperature (Tg) falls in arange of from 25 to 50° C. exceeds 50% of all the water-emulsiongranular resins, or when the water emulsion whose glass transitiontemperature (Tg) exceeds 50° C. is the granular resin, paint filmsbecome brittle because the formation of paint films is slow in bakingand drying, and accordingly cracks occur. Moreover, when it is less than20% of all the water-emulsion granular resins, or when the glasstransition temperature (Tg) is less than 25° C., the action of promotingthe evaporation of water is insufficient in the initial period of bakingand drying, and consequently swelling occurs in paint films which havesuch a heavy thickness as 8.0 mm.

[0086] Moreover, on the samples from which the normal paint films wereobtained, the damping property (loss factor) by means of a cantilevermethod was measured. As for the measurement of the damping property(loss factor), they were applied to a 10×220×0.8 (mm) steelplate so asto be 10×200×3.0 in superficial density (after being dried), and wereput in a drying oven, whose temperature was controlled at 140° C., for30 minutes to carry out baking and drying. After drying, the coatedplates were used as test plates for assessment, and were examined by acantilever method so as to calculate the loss factor at the secondaryresonance point by a half-width method. Table 3 sets forth the resultstogether with the measurement conditions. Excepting the case where thepaint film of Example No. 10 was examined at a measurement temperatureof 20° C., since all of the paint films exhibited a loss factor of 0.1or more, it is understood that they were good as a paint film and couldsecure stable performance at a measurement temperature of from 20° C. to40° C. TABLE 1 Gel Ratio Ex. No. 1 Ex. No. 2 Ex. No. 3 Comp. Ex. No. 1Comp. Ex. No. 2 Water 90% 100* Emulsion 80% 100* Resin 70% 100*(Styrene- 60% 100* Butadiene 50% 100* Copolymer) Tg: 5° C. (ResinousContent, 55%) Calcium Carbonate 400    200    400    200    400   200    400    200    400    200    Additives (Dispersing 20 20 20 20 20Agent & Running Inhibitor Agent) State of Dry 3.0 mm ◯ ◯ ◯ ◯ ◯ ◯ X X X XPaint (Swollen) (Swollen) (Swollen) (Swollen) Film after Dry 4.0 mm ◯ ◯◯ ◯ ◯ ◯ — — — — Baking and Dry 5.0 mm ◯ ◯ ◯ ◯ ◯ ◯ X X X X Drying**(Cracked) (Cracked) (Swollen) (Swollen) Dry 6.0 mm ◯ ◯ ◯ ◯ ◯ ◯ — — — —Dry 7.0 mm X X X X X X X X X X (Cracked) (Cracked) (Cracked) (Swollen)Swollen) (Swollen) (Cracked) (Cracked) (Swollen) (Swollen) Dry 8.0 mm XX X X X X — — — — (Cracked) (Cracked) (Cracked) (Swollen) (Swollen)(Swollen) Damping Measurement 0.15 0.14 0.14 0.15 0.14 0.15 — — — —Property Temp. 20° C. (Loss Measurement 0.14 0.12 0.14 0.14 0.15 0.13 —— — — Factor)*** Temp. 30° C. Measurement 0.11 0.10 0.11 0.10 0.11 0.11— — — — Temp. 40° C.

[0087] TABLE 2 Gel Comp. Ex. Comp. Ex. Comp. Ex. Ratio No. 3 No. 4 No. 5Water Emulsion 90% 100* Resin 80% 100* (Styrene- 60% 100* ButadieneCopolymer) (Tg: −5° C., Resinous Content: 55%) Water Emulsion 80% Resin60% (Styrene- 50% Butadiene Copolymer) (Tg: 30° C., Resinous Content:55%) Calcium Carbonate 400 200 400 200 400 200 Additives (Dispersing 2020 20 Agent & Running Inhibitor Agent) State of Paint Dry X X ◯ ◯ ◯ ◯Film after 3.0 mm (Cracked) (Swollen) Baking and Dry X X ◯ X ◯ XDrying** 4.0 mm (Cracked) (Swollen) (Swollen) (Swollen) Dry X X X X X X5.0 mm (Cracked & (Cracked & (Swollen) (Swollen) (Swollen) (Swollen)Swollen) Swollen) Dry X X X X X X 6.0 mm (Cracked & (Cracked & (Swollen)(Swollen) (Swollen) (Swollen) Swollen) Swollen) Dry X X X X X X 7.0 mm(Cracked & (Cracked & (Cracked & (Cracked & (Swollen) (Swollen) Swollen)Swollen) Swollen) Swollen) Dry X X X X X X 8.0 mm (Cracked & (Cracked &(Cracked & (Cracked & (Swollen) (Swollen) Swollen) Swollen) Swollen)Swollen) Damping Measurement — —    0.14    0.14    0.14    0.13Property (Loss Temp. Factor)*** 20° C. Measurement — —    0.09    0.08   0.10    0.08 Temp. 30° C. Measurement — —    0.04    0.03    0.05   0.04 Temp. 40° C. Gel Comp. Ex. Comp. Ex. Comp. Ex. Ratio No. 6 No. 7No. 8 Water Emulsion 90% Resin 80% (Styrene- 60% Butadiene Copolymer)(Tg: −5° C., Resinous Content: 55%) Water Emulsion 80% 100* Resin 60%100* (Styrene- 50% 100* Butadiene Copolymer) (Tg: 30° C., ResinousContent: 55%) Calcium Carbonate 400 200 400 200 400 200 Additives(Dispersing 20 20 20 Agent & Running Inhibitor Agent) State of Paint DryX X X X X ◯ Film after 3.0 mm (Swollen) (Swollen) (Swollen) (Swollen)(Swollen) Baking and Dry X X X X X X Drying** 4.0 mm (Cracked) (Cracked)(Cracked) (Cracked) (Cracked & (Cracked & Swollen) Swollen) Dry X X X XX X 5.0 mm (Cracked) (Cracked) (Cracked) (Cracked) (Cracked & (Cracked &Swollen) Swollen) Dry X X X X X X 6.0 mm (Cracked) (Cracked) (Cracked)(Cracked) (Cracked & (Cracked & Swollen) Swollen) Dry — — — — — — 7.0 mmDry — — — — — — 8.0 mm Damping Measurement — — — — —    0.06 Property(Loss Temp. Factor)*** 20° C. Measurement — — — — —    0.09 Temp. 30° C.Measurement — — — — —    0.15 Temp. 40° C.

[0088] TABLE 3 Ex. Ex. Ex. Ex. Ex. Ex. Ex. Comp. Comp. No. 4 No. 5 No. 6No. 7 No. 8 No. 9 No. 10 Ex. 9 No. 10 Styrene- Gel Ratio, 90%  80*  50*Butadiene Gel Ratio, 80%  80*  50*  80*  90* Copolymer Gel Ratio, 60% 80*  50*  40* Tg: 5° C. (Resinous Content, 55%) Styrene- Glass  20* 50*  20*  50* Acrylic ester Transition Copolymer Temp. (Tg), Gel Ratio,25° C. 10% Glass  20*  50*  10*  60* (Resinous Transition Content, Temp.(Tg), 52%) 50° C. Glass  20* Transition Temp. (Tg), 55° C. CalciumCarbonate 400 400 400 400 400 400 400 400 400 Additives (Dispersing  20 20  20  20  20  20  20  20  20 Agent & Running Inhibitor Agent) Stateof Dry 3.0 mm ◯ ◯ ◯ ◯ ◯ ◯ ◯ X X Paint (Cracked) (Cracked) Film after Dry4.0 mm ◯ ◯ ◯ ◯ ◯ ◯ ◯ X X Baking and (Cracked) (Cracked) Drying** Dry 5.0mm ◯ ◯ ◯ ◯ ◯ ◯ ◯ X X (Cracked) (Cracked) Dry 6.0 mm ◯ ◯ ◯ ◯ X ◯ X X X(Cracked) (Cracked) (Cracked) (Cracked) Dry 7.0 mm ◯ ◯ ◯ ◯ X X X X X(Cracked) (Swollen) (Cracked) (Cracked) (Cracked) Dry 8.0 mm ◯ ◯ ◯ ◯ X XX X X (Cracked) (Swollen) (Cracked) (Cracked) (Cracked) DampingMeasurement    0.13    0.12    0.14    0.11    0.12    0.15    0.09 — —Property Temp. 20° C. (Loss Measurement    0.17    0.15    0.18    0.14   0.16    0.15    0.12 — — Factor)*** Temp. 30° C. Measurement    0.15   0.18    0.14    0.17    0.15    0.12    0.19 — — Temp. 40° C.

1. A baking-drying water damping paint composition, comprising: a wateremulsion including at least one first granular resin selected from thegroup consisting of styrene-butadiene copolymers, acrylic estercopolymers and ethylene-vinyl acetate copolymers whose glass transitiontemperature is from 0 to 20° C. and gel ratio is from 60 to 80%; and aninorganic filler in an amount of 200 parts by weight or more withrespect to 100 parts by weight of said first granular resin.
 2. Thebaking-drying water damping paint composition set forth in claim 1,wherein a drying temperature of a paint film falls in a range of from 70to 160° C.
 3. The baking-drying water damping paint composition setforth in claim 1 comprising said inorganic filler in an amount of 600parts by weight or less with respect to 100 parts by weight of saidfirst granular resin.
 4. The baking-drying water damping paintcomposition set forth in claim 1, wherein said inorganic filler is atleast one member selected from the group consisting of calciumcarbonate, talc, diatomaceous earth, barium sulfate, zeolite, magnesiumcarbonate and mica.
 5. The baking-drying water damping paint compositionset forth in claim 4, wherein said inorganic filler has an averageparticle diameter of 50 μm or less.
 6. The baking-drying water dampingpaint composition set forth in claim 1, wherein said inorganic fillerincludes inorganic short fibers whose fibrous length is from 100 μm to 1mm.
 7. A baking-drying water damping paint composition, comprising: awater emulsion including at least one first granular resin selected fromthe group consisting of styrene-butadiene copolymers, acrylic estercopolymers and ethylene-vinyl acetate copolymers whose glass transitiontemperature is from 0 to 20° C. and gel ratio is from 60 to 80%, and atleast one second granular resin selected from the group consisting ofstyrene-butadiene copolymers, acrylic ester copolymers andethylene-vinyl acetate copolymers whose glass transition temperature isfrom 25 to 60° C.; and an inorganic filler in an amount of 200 parts byweight or more with respect to the sum of said first granular resin andsaid second granular resin taken as 100 parts by weight.
 8. Thebaking-drying water damping paint composition set forth in claim 7,wherein a drying temperature of a paint film falls in a range of from 70to 160° C.
 9. The baking-drying water damping paint composition setforth in claim 7 comprising said inorganic filler in an amount of 600parts by weight or less with respect to the sum of said first granularresin and said second granular resin taken as 100 parts by weight. 10.The baking-drying water damping paint composition set forth in claim 7,wherein said inorganic filler is at least one member selected from thegroup consisting of calcium carbonate, talc, diatomaceous earth, bariumsulfate, zeolite, magnesium carbonate and mica.
 11. The baking-dryingwater damping paint composition set forth in claim 10, wherein saidinorganic filler has an average particle diameter of 50 μm or less. 12.The baking-drying water damping paint composition set forth in claim 7,wherein said inorganic filler includes inorganic short fibers whosefibrous length is from 100 μm to 1 mm.
 13. The baking-drying waterdamping paint composition set forth in claim 7, wherein said firstgranular resin is included in an amount of from 40 to 85 parts by weightwith respect to the sum of said first granular resin and said secondgranular resin taken as 100 parts by weight.
 14. The baking-drying waterdamping paint composition set forth in claim 7, wherein said firstgranular resin is included in an amount of from 50 to 85 parts by weightwith respect to the sum of said first granular resin and said secondgranular resin taken as 100 parts by weight.